OSHA requirements are set by statute,
standards and regulations. Our interpretation letters explain
these requirements and how they apply to particular
circumstances, but they cannot create additional employer
obligations. This letter constitutes OSHA's interpretation of
the requirements discussed. Note that our enforcement guidance
may be affected by changes to OSHA rules. Also, from time to time
we update our guidance in response to new information. To keep
apprised of such developments, you can consult OSHA's website
athttp://www.osha.gov.

Thank you for your March 3, 2000 letter to the Occupational
Safety and Health Administration's (OSHA's) [Directorate
of Enforcement Programs (DEP)]. You have requested an
interpretation of 29 CFR 1910.24(c), Fixed Industrial Stairs,
Stair strength, in regards to the application of a 1000 lbs
load on fixed industrial stairs. Your questions are restated
below for clarity.

Question 1: What "strength to carry
safely" level is expected of the stair as far as resistance
to this load: Yield or allowable, i.e. to failure or to allowable
stresses used for steel design?

Reply: The design of fixed stairways and their components
must be based on their ultimate strength [yield stress (FY) or
ultimate stress (FU)] and not on the allowable stresses as given
in the Allowable Stress Design method of the American Institute
of Steel Construction, Ninth Edition.

Question 2: Where should it [1000 lbs load]
be applied: Stringers, Stair treads?

Reply: From a design standpoint, the specified design
loads (e.g., normal live load and moving concentrated load of
1000 lbs) must be placed where the maximum stress is experienced
by the individual structural components of the stair system.

Question 3: Is it a concentrated load or
spread over the whole stair tread area?

Reply: 29 CFR 1910.24(c) states; "Fixed stairways
shall be designed and constructed to carry a load of five times
the normal live load anticipated but never of less
strength than to carry safely a moving concentrated load
of 1,000 pounds" [emphasis added]. Therefore, with respect
to the design calculation, the normal live load is spread over
the whole stair tread area and the moving concentrated load is
considered to be a point load applied at a location on the stair
system where the maximum stress would be experienced by the
system (the 1000 lbs loading criteria is a minimum).

Thank you for your interest in occupational safety and health.
We hope you find this information helpful. Please be aware that
OSHA's enforcement guidance is subject to periodic review and
clarification, amplification, and correction. Such guidance could
also be affected by subsequent rulemaking. In the future, should
you wish to verify that the guidance herein remains current, you
may consult OSHA's website athttp://www.osha.gov. If you have any further questions, please feel
free to contact the [Office of General Industry Enforcement] at
202-693-1850.

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